This investigation is designed to follow prospectively a cohort of approximately 121,000 women, ages 30-54, in whom exposure to oral contraceptives, estrogens, cigarette, and hair dyes has been documented. Morbidity and mortality for a variety of cancers including breast, endometrial, ovary, lung and others, as well as cardiovascular events, will be followed. The approach is by mail questionnaire with further documentation of events by review of hospital records and pathologic specimen. The cohort was defined from the register of Registered Nurses collected by the American Nurses' Association in 1972 and recorded at that time as being married women. Those women who on Janualy 1, were between the ages of 30-55 and who responded to an inquiry in 1976 which collected - besides data mentioned above - information of menstrual history, height, weight, current contraceptive status and family history of myocardial infarction and breast cancer in female relatives constitute the cohort. In addition, an estimate of social class status at age 16, based on parental occupations was obtained. Personal past medical events related to cardiovascular, thromboembolic, benign and malignant breast disease, and other cancers were collected also. In 1980, a detailed dietary assessment was added to the questionnaire. These variables will be used in multivariate models to define levels of risk of the above-mentioned outcome events in 1982.